trade deficit fell sharply last month. the combination now has economists believing the economy grew in the last few months of 2012, even though data out last week showed the economy fell slightly in the fourth quarter. but a closer look shows some cause for caution. darren gersh reports. >> reporter: the december trade numbers were much better than forecasters expected. the deficit between what the u.s. exports and what we import fell 21% to $38.5 billion. and that means exports likely boosted growth in the last three months of 2012. >> so this is a good sign that exports were a little stronger than we thought when the numbers were first estimated and that is obviously a good sign for the economy. again, the economy is obviously growing way too slowly, but at least on this note, i think it will be revised upward. energy is a now a bright spot for the u.s. economy. thanks to new fracking technology, surging domestic production cut crude oil imports last year by 227 million barrels. but tt success was offset soewhat by impo